Surface Wetting

Wetting is the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. The degree of wetting (wettability) is determined by a force balance between adhesive and cohesive forces. Wetting deals with the three phases of materials: gas, liquid, and solid. It is now a center of attention in nanotechnology and nanoscience studies due to the advent of many nanomaterials in the past two decades.

  • A drop of water as a model for the interplay of adhesion and stiction

    A drop of water as a model for the interplay of adhesion and stiction picture 1 | Electrochemistry in a drop: Superposition of seven dynamic contact angle measurements of a drop of water on a surface; diameter of vertical tube capillary 0.85 mm. UZH

    Physicists at the University of Zurich have developed a system that enables them to switch back and forth the adhesion and stiction (static friction) of a water drop on a solid surface. The change in voltage is expressed macroscopically in the contact angle between the drop and the surface. This effect can be attributed to the change in the surface properties on the nanometer scale.

  • Added bacterial film makes new mortar resistant to water uptake

    Added bacterial film makes new mortar resistant to water uptake | The surface of the hybrid mortar (left) is covered with tiny crystalline spikes. This results in the so-called lotus effect which does not occur on the untreated mortar (right) Illustration: Stefan Grumbein / TUM

    Moisture can destroy mortar over time – for example when cracks form as a result of frost. A team of scientists at the Technical University of Munich (TUM) has found an unusual way to protect mortar from moisture: When the material is being mixed, they add a biofilm – a soft, moist substance produced by bacteria.

    Oliver Lieleg usually has little to do with bricks, mortar and concrete. As a professor of biomechanics at the Institute of Medical Engineering (IMETUM) and the Department of Mechanical Engineering, he mainly deals with biopolymer-based hydrogels or, to put it bluntly, slime formed by living organisms.These include bacterial biofilms, such as dental plaque and the slimy black coating that forms in sewage pipes. “Biofilms are generally considered undesirable and harmful. They are something you want to get rid of,” says Oliver Lieleg. “I was therefore excited to find a beneficial use for them.”

  • Surface wetting – tracking down the causes of polar hydrophobicity

    The question of whether a liquid beads or adheres to a surface plays a role in almost all branches of industry. Researchers from the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg and ExxonMobil Research & Engineering in New Jersey have now developed a multiscale simulation method for predicting the wetting behavior of liquids on surfaces. In a recent edition of the Journal of the American Chemical Society, the research team applied this methodology to the previously unexplained phenomenon of polar hydrophobicity in fluorinated carbon surfaces.